service engine soon light

simple · August 1, 2003

About 2 months ago my service engine soon light came on while I was driving. The light was not blinking, it was just on all the time. The truck also drove fine during this situation. I got a device to get the code and there was only one code which read there was a leak in the evaporative system. I thought that maybe my gas cap wasn't on tight enough, even though it was. I took the gas cap off and put it back on. (yes, I turned it until it clicked) About 2 days later the light went out and has been fine ever since yesterday. The light came back on again. I didn't hook something up to the the truck's computer because I don't have that piece of equipment anymore. I did what I did the last time with the gas cap, but it's been about the same amount of time and the light is still on. The truck still drives fine, you wouldn't even know that there's a problem. Keep in mind that I live in Wisconsin and we have emissions testing here. My stickers run out in August and I got something in the mail 2 weeks ago. I passed the test, and they even test your gas cap to see if it keeps pressure. That passed too. Any ideas as to what's going on here? I'm going to wait another day or two and if the light is still on I'll have it looked at.

AZ-Z71 · August 1, 2003

If you have an AutoZone near you (don't know if they are in your state) they will check the light for free. Mine has been doing this now for about two weeks but mine is supposedly the rear O2 sensor after the cat. Hopefully this weekend I'll change it out.

Tree_Hugger · August 1, 2003

Just because it was the gas cap last time doesn't mean it is this time.

If the lamp is not flashing, you can continue to drive.

Try disconnecting the battery for at least 35 minutes. This will probably clear the existing code, and you can see if the light comes back on again.

WEFs99 · August 2, 2003

Anyone that works on his own car needs a code scanner. Autozone has a good one for around $145. Autozone will check the codes free as has been said but if you get stuck with a shop doing it, the cost may be almost as much as a scanner.

99silveradoz71 · August 2, 2003

Had the ses light come on in my 99 a few weeks back out of nowhere. The truck ran fine and had no problems before that. Turned out to be a vent valve hose or such, which I noticed was above the tank between the cab and the bed.

frdfandc · August 2, 2003

My 03 has been in the shop twice in the last month for the check engine light being on. This last visit the truck has been at the dealer since this past Tuesday. It won't be ready till this up coming Monday. And it was the same evap system code I believe. I was told something about GM updating a part.

sjspor · August 2, 2003

If your SES sets, and it is the EVAP system, it will be a P0440 code... And if anyone figures out this bug.. let me know!! This should clear itself after either 3 or 5 sucessful

passes of the diag that checks the system.

I have lubed the seal on my cap, pulled the lines to the purge valve, checked the line to the engine. This is a true intermittent bug and it's making me nuts.

I suspect it is a piece of crud getting caught in the purge valve that is hopfully gone now after playing with the lines.

WEFs99 · August 2, 2003

Would these evap codes be covered under the extra long emissions warranty?

SportyShorty · August 3, 2003

I've got the same problem with my 99. Changed out the gas cap and light still came back on. I dont know about everyone else, but I'm getting tired of staring at that stupid SES light

frdfandc · August 3, 2003

The extra long emissions warranty is only provided by the Federal Government. This mostly includes (and might only be limited to) the PCM (computer brain) and the catalytic converters. It probably won't cover sensors & solenoids.

As far as the fix for mine, as soon as i find out exactly what they fixed, i'll post it up.

seadoons · August 4, 2003

It still be your gas cap - if you don't get it on tight enough, the light comes on. So you figure it out, and you tighten the cap. Cool. The lights stays on for a certain number of vehicle cycles (cold, hot, cold)....this is its way of checking to see if the problem is fixed. Just because the light went out in 2 days last time it doesn't mean it should go out in 2 days this time. It all depends on how many times your truck cycles. Maybe you drove it more last time?!?!

frdfandc · August 5, 2003

Picked up the truck today from the dealer. It was there since last tuesday. They ended up replacing the Evap Canister. Its supposed to be an updated part from GM. Here is the part number. 15175906.